This work aims to study plastic deformation inhomogeneity of laser-cladded flat samples under uniaxial tensile. High-nitrogen Cr-Mn-Ni austenitic stainless steel was chosen as the substrate material. Laser cladding was implemented by applying Ni-Cr-Fe + WC powder at varying laser power (1-2 kW) and scanning speed (0.008-0.035 m/s). The penetration depth of a single roller decreased with the increase in scanning speed. The microhardness exhibited wide ranging with the cladding thickness (from 700 to 1350 HV) and decreased with increasing scanning rate. The mechanical test data showed that the surface hardening of austenitic steel led to an increase in the tensile strength and a decrease in ductility. The effect of laser cladding modes on the degree of plastic flow inhomogeneity within the micro-volumes of the cladded layer and the surface was established using digital speckle photography. The local strain variation in the sample increased with an increase in the specific energy of laser cladding. The structural heterogeneity near the interface between the cladded layer and the substrate exerts an impact on the development regularity of localized plastic flow. Unfavorable choice of laser parameters leads to formation of micro-cracks and porosities in the microstructure.
The inhomogeneity of plastic deformation of laser cladding additively manufactured steel composites from low-carbon steel ASTM A414 grade A and stainless steel AISI 304 has been studied. The uniaxial tensile tests were carried out on flat samples with a thickness of 8 mm at a constant rate at room temperature after laser cladding and after six hours of heat treatment of specimens up to 900°C. The phase composition of the bimetal components was determined via X-ray diffraction. The effect of heat treatment conditions on the microhardness and plastic flow inhomogeneity near the bimetal junction zone has been established. The degree of plastic deformation inhomogeneity of different layers was quantitatively assessed using the coefficient of variation of local strains has been investigated via digital speckle correlation method. After laser cladding, the difference between the deformation inhomogeneities of the border zones near stainless and carbon steels was almost two times. The deformation inhomogeneity in the transition zone was shown to differ from those of the base layers, which affected the properties of bimetal products. The effect of structural heterogeneity near the interface of layers on the local strain distributions in the bimetal was discussed in present study.
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